LibHTML: Implement rendering

Libraries/LibHTML/RenderingContext.h

@@ -0,0 +1,16 @@
+#pragma once
+
+class GPainter;
+
+class RenderingContext {
+public:
+    explicit RenderingContext(GPainter& painter)
+        : m_painter(painter)
+    {
+    }
+
+    GPainter& painter() const { return m_painter; }
+
+private:
+    GPainter& m_painter;
+};